Signaling circuit



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E. D. JOHNSON ET AL SIGNALING CIRCUITS Original Filed March 2 3. 1921 Q a up w r W w w w ML. W w W. g a I n g w v n W a]. m li MT wfi rvhv w? Q& W W MMU i wk a Q .Q i g (C Patented Febt16, 1926.

UNITE STATES DGAR i). onnson, or EAST onanon, Ann CHARLES w. GREEN, or WYOMING, NEW

"PATENT OFFICE.

JERSEY, ASSIGNORS T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEXV 'YORK, N. Y., A CORPORATION (315 NEW YORK.

SIGNALING CIRCUIT.

Application filed March 22, 1921, Serial No. 454,830; Renewed August 14, 1925.

cuits and more particularly itrelat-es to re-' 'peater circuits of the two-way one repeater type with which is associated means for relaying ringing current or other signaling current as distinguished from telephonecurrents. V

One of the objects of the invention is to provide means for associating a source ofriiigingcurrent with one line upon the receipt' of ringing current from another line, protecting the repeater from the incoming and relayed ringing currents While preventing any of the incoming current from pass ing directly to the other line, and for disconnecting the source of ringing current upon the cessation of theincoming ringing current. 1 i

As is well known in the art, the usual method of connecting" a two-way one repeater'iii a telephone circuit is to connect the two line sections by a so-called threewinding transformer, one winding of which is included iiione line'section, a second *inding inthe second line section, and the thiru winding being connected to the output of the repeater, while connections for the input of the repeater are taken from points intermediate the first two windings. Vith such an arrangement, incoming telephone currents from either line section are im pressed upon the input of the repeater and the amplified currents are impressed by the three winding transformer upon both line sections. g V This invention provides an arrangement for sending ringing current overon'e line 4 section when ringing current is present in,

the other line section in cases where it is not found desirable to send the ringing curreiits'through therepeater in the same manner as the speech currents. The arrangenieiitb irfiy comprises ringing responsive currents to the other line section.

relay individual to each line section which,

such values as to offer high impedance to ringing currents while offering negligible impedance to currents of speech frequencies, so that'incoming ringing currents from one i line section cannot pass through the threewindiiig transformer and cause the false op-' ei'ation of the ringing responsive relay associated with the other line section. In order to prevent any of the incoming ringiug currents from getting into the input of the repeater and thereby being amplified, an anti-resonant circuit is. connected, in series with the input leads of the repeater and tuned to the ringing currents so that for currents of ringing frequencies the input leads of the repeater offer a very high impedance. As an additional precaution for preventing the amplification of the locally generated ringing currents whichare of much greater strength than the weak incoming ringing currents it is generally necessary to provide a relay under the control of the ringing responsive relay foriopening the input connections to the repeater during the connection of the local source of ringingcurrents to either line section. Inasmuch asthe three-winding transformer arrangementabove described is essentially a balanced network of the iVheatstone bridge type in which each line section constitutes an arm, the third arm consisting of the input connections to the repeater, and the fourth arm the output connections of the repeater, it is essential that this breaking of the input leads should not appreciably affect the balance of this network. it has been found, for example, that when a potentiometer and a filter are included between the midpoints of a three-winding transformer and the input transformer of the repeater that the balance of the network is not appreciably changed if the circuit is broken at such a point that the filter and the potentiometer are located between the point of breaking and the inidpolnts of the three-winding transformer.

The-invention will be better understood lay and the three-winding transformer of by reference to the following detailed description taken in connection with the accompanying drawing in which Figure 1 represents a twoway one repeater circuit embodying this invention and Figure 2 represents the transmission characteristic curve of the repeater of this invention.

Referring to Figure of the draw ng, the two-way one repeater disclosed therein comprises two line sections 10 and 11, preferably'of approximately the same impedance, which are connected together by a three-winding transformer, wmdrng 12 of which is included in series with line sectionlO, while winding 13 is included in line section 11. v The third winding 14 of the transformer is coupled to the output terminals of a vacuum tube repeater 15 of the type now well known in the art. The input leads 16 for the repeater are connected to the mid-points of the windings 12 and 13 of the three-winding transformer. These leads include the usual wave 'filter17 and a gain adjusting potentiometer18 which are located between the above mentioned midpoints and the input transformer 19 0f the repeater.

The operation of such an arrangement for speech frequencies is now well known in the art and may be described briefly by notmg that incoming speech currents from either line section are impressed by the input leads 16 through the wave filter 17 and the input transformer 19 upon the input terminals of F the vacuum tube repeater 15. The amplilied currents in the output circuit of repeater 15 by the three-winding transformer are impressed serially upon both line sections.

In providing ringing arrangements for a telephone line in which repeaters are employed, it is frequently preferable to relay the ringing currents around the repeaters instead of having the ringing currents amplitied directly by the repeaters as is done for the telephone currents. This relayed ringing is particularly preferable for telephone lines in which a plurality of spaced repeaters are employed on account of limitations in the power capable of being handied by two vacuum tubes connected in tandem of the type now employed in telephone lines.

The relayed ringing arrangement of this invention comprises a ringing responsive relay 25 connected in shunt to line section 10 and a ringingresponsive relay 26 connected in shunt to line section 11. Connected in shunt to each line section is a circuit containingcapacities 28 and and inductance 29 tuned to the frequency of the incoming ringing currents so that the shunt is of low impedance for ringing currents but of extremely high impedance for currents of other frequencies, such as the speech he at their ends quencies. Each ringing responsive relay is, connected in shunt to the large condenser 85}.

Assuming that an operator at a distant; stati'on'connected to line 10, wishes to ring; a station connected at the other end of line-- 11, incoming ringing currents from line 10 cause relay 25 to operate and break the holding circuit for relay. 30 which holding; circuit, in the absence of ringing currents, may be traced from grounded battery, Winding of relay-30, conductor 31 and contact of relay 25 to ground. The breaking of this holding circuit for relay 30 allows its'contact to fall back and close the following circuit from ground, battery, winding of relay 32, conductors 33 and 34, windingof relay 35, conductor 36, contact of relay 30, conductor 37, winding of relay 38 and contact of relay 39 to ground, thereby energizing relays 32, 35 and 38. Relay 32 on being energized by the closing of the circuit just traced pulls up its movable contact '40 and opens the input connections of the repeater; between the potentiometer 18 and the pri-v marywinding of the input transformer 19 thereby preventing the possibility of any of the ringing current from getting into, the input of the repeater. Relay 35 on being; energized pulls up its movable contacts and{ breaks the connections between line section 11 and the three-windingtransformer and connects the line section 11 instead to leads; 41. Relay 38 in operating, connects a suit-. able source of ringing current 42 through leads 43 and 41, and the contacts of energized relay 35 to line section 11 so that incoming ringing currents in line section 10. serve to connect source 42 to line section 11.,

If, on the other hand, the incoming ring ing currents originate in line section 11, ringing responsive relay 26 will break the holding circuit for relay 44 which is non mally closed and may be traced from ground, battery, winding of relay 44, conductor 45, and contact of relay 26'to ground. The deenergization of relay 44 allows its movable contact to fall back and close the following circuit from ground, battery, winding of relay 32, conductors 33 and 47, winding of relay 48, conductor 49', contactof deenergized relay 44, conductor 37, wind ing cfrelay 38, and contact of relay 39 to ground. Relay 32 operates, as in the pre vious case, to open the input leads of the repeater while relay 48 disconnects line 7 section 10 from the threewinding transformer and relay 38 serves to connect the source of" ringing current 42 through the closed contacts of relay 48 to line section 10.

Upon the cessation of incoming ringing currents from either line section, the holding circuit for relay 30 or relay 44, as the case may be, is closed again thereby deenergizing relays 32, 38, and 35 or 48, as the case may be, so that the repeater is in a condition to amplify any incoming speech currents from sponding condensers 52 and 53 are similarly ing frequencies.

located between the three-winding transformer and the ringing responsive relay 26. These condensers should have such values as to be of high impedance for the ringing currents but of low impedance to speech currents. For example, if the ringing currents are of 135 cycles, each of these condensers should have an approximate value of 1 1n.tf.

The breaking of the input leads of the repeaterby relay 32 should preferably take place at a point remote from the midpoints of'the three-winding transformer in order to prevent thebreaking from upsetting the balanced condition which, as is well known existsbetween the two linesections, the output of the repeater and the input of the repeater. In the drawing, for example, the breaking is shown to take place at such a point'that the input potentiometer 18 and shunt impedances 54 and 55 of the wave filter 17 intervene between the point of breakage and the midpoints of the threewinding transformer. It has been found in such a case that the breaking of the input leads has a negligible effect on the balanced condition of the three-winding transformer because opening and closing the in ut leads at this point produces a very sma 1 change inthelmp'edance of the input lea'ds looking from the midpoints of the three winding erabletoinclude resistance elements 62 and 63 in series therewith to prevent the antiresonant circuit from appreciably affecting the transmission characteristic of the repeater for frequencies higher than the mug- Referring to Fig. 2, curve A represents the transmission characteristic 'which itis desired the repeater should have for currents of frequencies from 135 cycles on. The horizontalaxis 1n this figurerepresents various frequencies, while the vertical axis represents'the miles gain or amplification produced by the repeater. lVhen, however, an anti-resonant circuit is included in series with the primary winding of the input transformer and tuned to 135 cycles for example, there is a hump in the t'ansmission characteristic curve which takes place for frequencies in the neighborhood of 300 cycles, such as shown at point B in Fig. 2. It has been found that this undesired gain in the transmission for frequencies of the order of 300 cycles may be eliminated by including resistance elements of sufiicient value in series with the anti-resonant circuit. In one case, for example, where ringing'currents were 135 cycles, it was found that the proper value of each of these resistances was approximately 100 ohms.

As is well known in the art a repeater in a slightly unbalanced circuit will tend to sing at that frequency for which it gives the greatest gain. The elimination of the peak at 300 cycles therefore prevents the repeater singing at 300 cycles under conditions where singing would not take place for other frequencies. In other words, the elimination of this peak will allow a greater unbalance of the repeater circuit without singing of the repeater being produced thereby.

As is usual in such repeater circuits, transformers 71 and 72 are provided for permitting the repeater attendant to monitor or test over line sections 10 and 11 whenever desired. VVindings 7 and 7st of transformers 71 and 72 are connected in series with leads 75 which are normally shortcircuited between the two spring contacts of the monitoring jack 76. \Vhenever the repea er attendant desires to monitor, a plug 77 is inserted in jack 76 so that leads 7;) from. the monitoring coils are electrically connected to leads 78 which may lead to the attendants telephone set. lVhenever the repeater attendant desires to cut out repeater 15 and send ringing current from conductors 78 to the line sections 10 and 11, he connects ground by a key (not shown) to lead 79, and by plug 75 and jack 76, grounds conductor 80 which leads through the winding of relay 81 and winding of relay 39 to battery and ground. This grounding of conductor 80 energizes relays 59 and 81. The energization of relay 39 closes the following circuit: ground, battery, winding of relay 32, conductors 33 and 34, winding of relay 35, conductor 36, inside contact of relay 39 to ground, and from ground, battery, winding of relay 32. coir ductors 33 and d7, winding of relay 48, conductor 4-9, and outside contact of relay 3%) to ground. The energization of both relays 35 and 4:8 disconnects the two line sections 10 and 11 from the three-winding transformer and instead directly connects them through leads 41 to each other. The conductors 78 of the repeater attendants telephone set are also directly'connected through the contacts of relay 81 to both line sections, so that ringing current applied to conductors 78 by the repeater attendant will be transmitted from conductors 78 toboth line sections. Removing ground, however, from lead will restore the relays to their normal condition so that repeater 15 is made responsive to-speech currents from either line section and the ringing responsive relays 25- and 26 are again adapted to connect the source or ringing currents 42 to one line section in response to ringing currents in the other line section. I

It is to be understood that this invention is not limited to the particular embodiment above described but that the invention may possess widely different forms without departing, in any wise from the spirit of the invention as defined in the appended claims.

lVhat is claimed is:

1. In an electric system, two real line sections directly connected without the intermediary of balancing artificial lines, and a repeater station comprising a repeater element, a three-winding transformer having one winding in circuit with one line section, a second winding in circuit with the second line section, and a third winding connected to the output of said repeater element, a connection from a point intermediate said first two windings to the input of said repeater element,-a source of signaling currents other than speech currents at said station, ineans'responsive to signaling currents from one line section for impressing currents from said source upon said second line section, and an anti-resonant circuit inshunt tosaid connection to the input of said repeater and tuned to a frequency corresponding to the frequency of said signaling currents whereby currents of said signaling frequency are prevented from being impressed on said repeater. I I

2. In an electric system, two real line sections directly connected without the intermediary of balancing artificial lines, and a repeater station comprising a repeater element, a three-winding transfo mer having one winding in circuit with one line'section, a second winding in circuit with the second line section, and a third winding connected to the output of said repeater element, a connection from a point intermediate said first two windings to the in'put'of said re? peater element, a source of signaling cur-, rents other than speech currents at said station, means responsive to signaling currents from one of said line sections for-inipressing currents from said source upon the other line section, an impedance in shunt to said connection to the input of said repeater, and means responsive to incoming signaling the second line section, and a third winding connected to the output of said repeater element, a connection from a point intermediatesaid first two windings connected to the input of-said repeater element, a source of signaling currents other than speech currents at said stat-ion, means responsive to signaling currents from one line section for impressing currents from said source upon the other line section, and means responsive to incoming signaling currents for preventing said repeater ele ment from receiving currents of any frequency while leaving substantially unchanged the apparent impedance of the input of said repeater measured from themidpoint of said first two'windings and looking in the direction of the input of the repeater.

4. In an electric system, two real line seetions,.a repeater element for repeating from one line section to anothersignaling currents of one type, a source of signaling currents of a second type, means responsive to incoming signaling currents of the second type in one line section for connecting said source to the second line section, an electrical network associated with said repeater for-preventing currents of the fre quency of said second type from being impressed on said repeater, said network tending to appreciably atiect the transmission characteristic of saidrepeater for current: of said first type, and means for substantially overcoming the tendency of saidnetwork to distort the transmission characteristic of said repeater; i

5. In an electric system two realline seetions, a repeater element having its input terminals associated with one line section and its output terminals associated with the second line section for repeating between the line sections signaling currents ofone type, a source of signaling currents of another type, means responsive to incoming signaling currents of the second type in one line section for connecting said source. to the second line section, an 'antifresonant circuit veffectively in series with the input te "minals of said repeater and tuned to the frequency of the currents of said source,

and means'for overcoming the tendency of said anti-resonant circuit to distort the transmission characteristic of said repeater.

'6. In a telephone system, two line sections adapted to be supplied with currents of speech frequencies and ringing currents,

a repeater for repeating the speech currents from one line section 'tothe other, and means comprising an anti-resonant circuit effectively in series with the input terminals of said repeater and tuned to the frequency of said ringing-currents for preventing said ringing current from being impressed on said repeater while leavingsubstantially unchanged the transmission characteristic of said repeater for the speech impressing signaling currents of a second type upon one line section when signaling currents of said second type are present in the other line section, means offering high impedance to currents of said second type for preventing currents of said second type from being impressed on said repeater, said last means tending to appreciably affect the transmission characteristic of said repeater fort-he type of currents to be transmitted therethrough, and means for preventing saidlast named means from appreciably affecting the transmission characteristic of said repeater for currents of certain frequencies other than the frequencies of the currents of said second type.

8. In an electric system, two line sections, a repeater having input terminals associated with one line section and output terminals associated with the second line section whereby said repeater is adapted to repeat between said lino sections, signaling currents of one type, means for impressing upon one line section signaling curroute of a second type when currents of said second type are present in the other line sec tion, an anti'resonant circuit tuned to the frequency of the currents of said second type and connected efiectively in series with the input terminals of said repeater, and a resistance element connected to said antiresonant circuit for preventing said antiresonant circuit from appreciably affecting the transmission characteristic of said repeater for currents of certain frequencies other than the frequency of said currents of the second type.

9, In an electric system, two line sections adapted to be supplied with signaling currents and ringing currents, a repeater element, connectionstrom one line section to the input terminals of said rep-eater, connectionsfrom the output terminals of said repeater to the second line section whereby said repeater is adapted to repeat said signalingcurrents between said line sections, a source of ringing-current, means responsive to ringing currents in one line section for connecting said source to said second line section and for breaking the connections to the input of said repeater, an anti-resonant circuit in series with the input terminals of said repeater and tuned to the frequency of the ringing currents in said first line, and a condenser located electrically between said ringing current responsive means and the input terminals of said repeater, said condenser ofl'ering a high impedance to ringing currents but negligible impedance to said signaling currents.

10. In an electric system, an incoming line, a second line of approximately the same impedance as said incoming line, a three-winding transformer having one wind ing in circuit with said incoming line, a second winding in circuit with said other line, repeaterinput terminals, repeater output terminals, a connection from the midpoint of said first two windings to one set of said terminals, a connection from said third winding to the other set of said terminals, a shunt impedance in one of said connections, and means responsive to signaling currents in one of said lines for breaking said last mentioned connection between said shunt impedance and the repeater terminals.

11, In an electric system, an incoming line adapted to be supplied with signaling currents and ringing currents, a second line oi": approximately the same impedance as said incoming line, a three-winding transformer having one winding in circuit with said incoming line, a second winding in circuit with said other line, repeater input terminals, repeater output terminals, a connection from the midpoint of said first two windings to one set of said terminals, a connection from said third winding to the other set of said termanls, a shunt impedance in one of said connections, and means responsive to the ringing currents in said incoming line for breaking said last mentioned con nection between said impedance and the repeater terminals.

12. In an electricsystem, an incoming line adapted to be supplied with signaling currents and ringing currents, a second line of approximately the same impedance as said incoming line, a three-winding transformer having one winding in circuit with said incoming line, a second winding in circuit with said other line, repeater input terminals, repeater output terminals, a connection from the midpoint of said first two windings to one set of said terminals, a connection from said third winding to the other set of said terminals, and an anti-resonant circuit in series with one of said connections and tuned to the frequency of said ringing currents.

13. In an electric system, an incoming line adapted to be supplied With signaling cur rents and ringing currents, a second line of approximately the same impedance as said incoming line, a three-Winding transformer having one Winding in circuit With said incoming line, a second Winding in circuit With said other line, repeater input terminals, repeater output terminals, a connection from the midpoint of said first two windings to one set of said terminals a connection from said third winding to the other set of said te'minals, a shunt impedance in one of said connections, an anti resonant circuit in series with one of said connections and tuned to the frequency of said ringing currents, and means for preventing said anti-resonant circuit from appreciably affecting the transmission characteristic of the system for frequencies greater than the ringing currents.

14.1%. system comprising a repeater, a

source for supplying to said repeater electrical variations to be repeated, and means for modifying the transmission characteristic of the repeater, said means comprising a capacity, an inductance and a resistance,

said capacity and inductance being connected to, form a loop circuit, and said resistance and said loop circuit being connected in series with each other with respect to said source and said repeater.

15. In combination, a line, a second line, a repeater having input and output terminals connected to *said lines in conjugate relation, and means responsive to a condition of one of said lines for interrupting one of the connections between said terminals and said lines at such a point in said one connection that the conjugate relation of the lines and the repeater is maintained.

In Witnesswhereof, We hereunto subscribe our names this 21 day of March A. D., 1921.

CHARLES W. GREEN. EDGAR D. JOHNSON. 

